Search:

so , looking at csr water pumps via google images it would seem our pumps aren't so much , "wrong" as they are "the way" csr does their impellers
it would appear they ALL have the same twist to the...

looking at mine it appears the impeller is threaded onto the shaft
simply hitting the thread/edge of impeller two or three times to stake the impeller to the shaft should be sufficient (I'D think)
...